test(checks): cover three untested edge cases in runChecks

[protosphinx]

Why

src/checks.ts has three code paths that had no test coverage. The config.mcpServers.size > 0 guard (documented in the README as "if neither settings.json exists, MCP server warnings are skipped") was exercised only indirectly. The description-collision negative path (Jaccard below 0.6) and the directory-name branch of name-drift were also absent from the suite.

What

• Add test: skips mcp-server-unknown when mcpServers set is empty - verifies the size > 0 guard prevents a false positive on fresh checkouts with no settings.json
• Add test: does not fire description-collision when Jaccard is below threshold - negative path for the Jaccard collision detector
• Add test: does not flag name-drift when name matches the directory - the dirBase branch of the name-drift OR condition

Tests

• File changed: test/checks.test.ts (+37 lines, 0 new dependencies)
• Suite went from 70 to 73 passing tests
• All 9 test files pass: vitest run clean

Self-merge gate

• all CI checks pass
• LOC delta < 250 (added + removed)
• no public-API surface change
• no runtime-dependency additions
• no workflow file changes
• tests added or extended

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Generated by Claude Code